Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$207.31	8.585%	$225.1076	$225.11	$225.10	$225.10
Purchase #2	$201.49	4.442%	$210.4402	$210.44	$210.45	$210.40
Purchase #3	$74.39	5.240%	$78.288	$78.29	$78.30	$78.30
Purchase #4	$95.86	6.277%	$101.8771	$101.88	$101.90	$101.90
Purchase #5	$230.54	8.241%	$249.5388	$249.54	$249.55	$249.50
Purchase #6	$208.73	9.468%	$228.4926	$228.49	$228.50	$228.50
Purchase #7	$131.47	6.196%	$139.6159	$139.62	$139.60	$139.60
7 purchase totals =	$1,149.79		$1,233.3602	$1,233.37	$1,233.40	$1,233.30